Chromosomal localization of complex and simple repeated human DNAs

Complex repeating restriction multimers and a simple AT rich satellite isolated with Hoechst 33258 (<= 0.5% of the human genome) were localized by in situ hybridization to human chromosomes. The complex repeats were clustered at the centromeres, consonant with their integration in tandem arrays at these loci; these sequences were very prominent on chromosomes 7, 10 and 19, sites not previously identified with any specific human repeated sequence. The Hoechst simple satellite labelled predominantly the long arms of the Y chromosome. Although this simple satellite and the complex restriction multimers did not hybridize with each other, and did not contain detectable ribosomal sequences, both isolates additionally labelled the nucleolus organizing regions (NORs) of acrocentric chromosomes. —The possible relationship of complex and simple repeated DNAs, and their assignment to specific chromosomal domains, is discussed.